U.S. patent number 8,717,518 [Application Number 13/054,380] was granted by the patent office on 2014-05-06 for polarization plate and liquid crystal display.
This patent grant is currently assigned to LG Chem, Ltd.. The grantee listed for this patent is Yeong Rae Chang, In Cheon Han, Kyung Ki Hong, Hyo Jin Jeong, Soon Hwa Jung, Ju Young Kim, Kee Young Kim, Se Ra Kim, Sung Su Kim, Eun Sang Yoo. Invention is credited to Yeong Rae Chang, In Cheon Han, Kyung Ki Hong, Hyo Jin Jeong, Soon Hwa Jung, Ju Young Kim, Kee Young Kim, Se Ra Kim, Sung Su Kim, Eun Sang Yoo.
United States Patent |
8,717,518 |
Kim , et al. |
May 6, 2014 |
Polarization plate and liquid crystal display
Abstract
The present invention relates to a polarizer having an
antistatic layer and a liquid crystal display. The present
invention may provide a polarizer which may prevent malfunction of
devices by static electricity generated in preparation or use
procedures even without using the ITO layer conventionally formed
between the upper glass substrate of a liquid crystal panel and a
polarizer in a liquid crystal display for an antistatic purpose,
and has excellent physical properties such as endurance reliability
under high temperature or high humidity condition and optical
characteristics, and a liquid crystal display thereof.
Inventors: |
Kim; Se Ra (Daejeon,
KR), Jung; Soon Hwa (Daejeon, KR), Kim; Kee
Young (Daejeon, KR), Kim; Sung Su
(Chungcheongbukdo, KR), Hong; Kyung Ki
(Chungcheongbukdo, KR), Jeong; Hyo Jin (Cheonan-si,
KR), Yoo; Eun Sang (Chungcheongbukdo, KR),
Han; In Cheon (Seoul, KR), Chang; Yeong Rae
(Daejeon, KR), Kim; Ju Young (Daejeon,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kim; Se Ra
Jung; Soon Hwa
Kim; Kee Young
Kim; Sung Su
Hong; Kyung Ki
Jeong; Hyo Jin
Yoo; Eun Sang
Han; In Cheon
Chang; Yeong Rae
Kim; Ju Young |
Daejeon
Daejeon
Daejeon
Chungcheongbukdo
Chungcheongbukdo
Cheonan-si
Chungcheongbukdo
Seoul
Daejeon
Daejeon |
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A |
KR
KR
KR
KR
KR
KR
KR
KR
KR
KR |
|
|
Assignee: |
LG Chem, Ltd. (Seoul,
KR)
|
Family
ID: |
41817891 |
Appl.
No.: |
13/054,380 |
Filed: |
July 17, 2009 |
PCT
Filed: |
July 17, 2009 |
PCT No.: |
PCT/KR2009/003963 |
371(c)(1),(2),(4) Date: |
April 12, 2011 |
PCT
Pub. No.: |
WO2010/008239 |
PCT
Pub. Date: |
January 21, 2010 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20110181813 A1 |
Jul 28, 2011 |
|
Foreign Application Priority Data
|
|
|
|
|
Jul 18, 2008 [KR] |
|
|
10-2008-0070110 |
May 27, 2009 [KR] |
|
|
10-2009-0046491 |
|
Current U.S.
Class: |
349/96;
359/492.01; 349/122; 349/141 |
Current CPC
Class: |
G02B
5/3058 (20130101); G02F 1/133528 (20130101); G02F
2202/28 (20130101); G02B 5/30 (20130101); G02F
2202/22 (20130101); G02F 2201/38 (20130101) |
Current International
Class: |
G02F
1/1335 (20060101); G02F 1/1343 (20060101); G02B
5/30 (20060101); G02F 1/1333 (20060101) |
Field of
Search: |
;349/96,122,141
;359/492.01 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101051144 |
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Oct 2007 |
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CN |
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11-091038 |
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Apr 1999 |
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JP |
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2003-154616 |
|
May 2003 |
|
JP |
|
2007-041598 |
|
Feb 2007 |
|
JP |
|
2007-045917 |
|
Feb 2007 |
|
JP |
|
2008-152245 |
|
Jul 2008 |
|
JP |
|
10-2006-0012441 |
|
Feb 2006 |
|
KR |
|
10-2006-0115168 |
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Nov 2006 |
|
KR |
|
10-2007-0074343 |
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Jul 2007 |
|
KR |
|
10-2008-0027565 |
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Mar 2008 |
|
KR |
|
594233 |
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Jun 2004 |
|
TW |
|
200537140 |
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Nov 2005 |
|
TW |
|
200628493 |
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Aug 2006 |
|
TW |
|
200702756 |
|
Jan 2007 |
|
TW |
|
200708547 |
|
Mar 2007 |
|
TW |
|
WO 2007/029936 |
|
Mar 2007 |
|
WO |
|
WO 2007/029936 |
|
Mar 2007 |
|
WO |
|
Primary Examiner: Qi; Mike
Attorney, Agent or Firm: McKenna Long & Aldridge,
LLP
Claims
The invention claimed is:
1. A liquid crystal display comprising: an IPS mode liquid crystal
panel comprising an upper substrate and a bottom substrate, which
are apart from and opposite to each other; a liquid crystal layer;
a polarizer comprising a polarizing film or a polarizing element; a
protective film formed on the upper part and the bottom part of
said polarizing film or polarizing element; and a pressure
sensitive adhesive layer having a surface resistance of
10.sup.12.OMEGA./.quadrature. or less formed on the bottom part of
said bottom protective film; and an antistatic layer having a
surface resistance of 2.times.10.sup.8 to
4.times.10.sup.9.OMEGA./.quadrature. formed on the upper or bottom
part of said protective film, wherein both of a common electrode
and a pixel electrode are formed on the bottom substrate, and the
liquid crystal layer is operated by a horizontal electrical field
generated by the common and pixel electrode, and wherein the
polarizer is directly attached on the upper substrate, on which a
conductive layer for antistatic purpose is not formed.
2. The liquid crystal display according to claim 1, wherein the
antistatic layer is formed on the upper part and the bottom part of
the protective film.
3. The liquid crystal display according to claim 1, wherein the
antistatic layer comprises a binder resin and a conductive
material.
4. The liquid crystal display according to claim 3, wherein the
binder resin is a light curable binder resin.
5. The liquid crystal display according to claim 4, wherein the
light curable binder resin is a cured product of a resin
composition comprising a multifunctional monomer or oligomer; and a
photoinitiator.
6. The liquid crystal display according to claim 5, wherein the
multifunctional monomer or oligomer is a multifunctional
acrylate.
7. The liquid crystal display according to claim 5, wherein the
resin composition comprises 1 to 20 parts by weight of the
photoinitiator, relative to 100 parts by weight of the
multifunctional monomer or oligomer.
8. The liquid crystal display according to claim 3, wherein the
conductive material is a metal, a metal oxide, a metal alloy or a
conductive polymer.
9. The liquid crystal display according to claim 3, wherein the
conductive material comprises one or more selected from the group
consisting of ITO, AZO, ATO, SnO, RuO.sub.2, IrO.sub.2, gold,
silver, nickel, copper, palladium, polyaniline, polyacetylene,
polyparaphenylene, polypyrrole, polythiophene, polydienylene,
polyphenylene vinylene, polyphenylene sulfide and
polysulfurnitride.
10. The liquid crystal display according to claim 3, wherein the
antistatic layer comprises 10 to 80 parts by weight of the
conductive material, relative to 100 parts by weight of the binder
resin.
11. The liquid crystal display according to claim 1, wherein the
pressure sensitive adhesive layer has the gel content, represented
in the following Equation 1, of 5% to 95%: Gel Content
(%)=B/A.times.100 [Equation 1] wherein, A represents weight of said
conductive pressure sensitive adhesive, and B represents dry weight
of undissolved conductive pressure sensitive adhesive after
immersing it in ethyl acetate at room temperature for 72 hours.
12. The liquid crystal display according to claim 1, wherein the
pressure sensitive adhesive layer is a cured product of a
composition comprising a pressure sensitive base resin and an
antistatic agent.
13. The liquid crystal display according to claim 12, wherein the
pressure sensitive base resin has a weight average molecular weight
of 800,000 to 2,000,000.
14. The liquid crystal display according to claim 12, wherein the
pressure sensitive base resin has a glass transition temperature of
-60.degree. C. to 15.degree. C.
15. The liquid crystal display according to claim 12, wherein the
antistatic agent is an organic or inorganic salt.
Description
This application is a National Stage Entry of International
Application No. PCT/KR2009/003963, filed Jul. 17, 2009, and claims
the benefit of Korean Application Nos. 10-2008-0070110, filed on
Jul. 18, 2008, and 10-2009-0046491, filed on May 27, 2009, which
are hereby incorporated by reference for all purposes as if fully
set forth herein.
TECHNICAL FIELD
The present invention relates to a polarizer and a liquid crystal
display thereof.
BACKGROUND ART
A liquid crystal display is a device displaying a picture by
inserting liquid crystals two sheets of thin transparent
substrates. In the liquid crystal display, liquid crystals change
their molecular arrangement as voltage is applied via electrodes
connected thereto, so that light transmission may be varied to
display a picture or a color. The liquid crystal display has
advantages of being low power consumption and being capable of
sheeting it flat, and thus is now in the limelight of various
fields.
The liquid crystal display may be classified into electrical
driving scheme and optical driving scheme according to a driving
scheme. A representative example of the optical driving scheme is
SLM (spatial light modulator), in which the liquid crystal display
is controlled by optical signals.
Meanwhile, the electrical driving scheme may be classified into
passive matrix type and active matrix type depending on the
presence of active elements on driving pixel electrodes.
The passive matrix type may be classified into TN-LCD (twisted
nematic-LCD), STN (super twisted nematic-LCD), F-LCD
(ferroelectic-LCD) and PD-LCD (polymer dispersed-LCD), according to
types of liquid crystals, and the active matrix type may be
classified into two terminal type and tree terminal type, according
to number of terminals.
In addition, the above two terminal type generally uses MIM
(metal-insulator-metal) type or diode type, and the tree terminal
type generally uses thin film transistors.
The active matrix liquid crystal display has a color filter
substrate (upper transparent substrate), on which common electrodes
are formed; an array substrate (bottom transparent substrate), on
which pixel electrode are formed; and a liquid crystal panel
comprising liquid crystals interposed between said two substrates.
This display is such a type that the common electrodes and the
pixel electrodes drive liquid crystals by electric field applied up
and down, and has excellent transmittance, aperture ratio,
resolution and capability for representing moving images.
Meanwhile, to improve viewing angle characteristics, some liquid
crystal displays, such as multi-domain liquid crystal display,
compensation film liquid crystal display, vertical alignment liquid
crystal display (VA-LCD) and in-plane switching liquid crystal
display (IPS-LCD), have been developed.
The IPS mode of the above displays is suitable to large area
displays such as monitors, and has an advantage that all viewing
angles are wide in the left, right, top and bottom directions.
In this IPS mode, a liquid crystal panel has the upper substrate of
a color filter substrate and the bottom substrate of an array
substrate, which are apart from each other, and opposite to each
other, and has a liquid crystal layer interposed between said upper
and bottom substrates. On said upper substrate, a black matrix is
formed, which serves to interrupt light leakage, in a form of
matrix, and red, green and blue layers are formed, sequentially and
repeatedly, at regions corresponding to pixel regions,
respectively, and an overcoat layer is usually formed thereon. On
said bottom substrate, common electrodes and pixel electrodes are
formed, whereby the liquid crystal layer operates by horizontal
electrical field with the common electrodes and the pixel
electrodes.
Generally, said various liquid crystal displays have a structure as
represented in FIG. 1. Specifically, the liquid crystal display has
a liquid crystal panel comprising a liquid crystal layer (1) and
the upper and bottom substrates (for example, a glass substrate
such as a color filter substrate and an array substrate) (2-1,
2-2), and also comprises the upper polarizer (3) formed on the
upper part of said liquid crystal panel and the bottom polarizer
(not represented therein) formed on the bottom part thereof.
A polarizing film (or polarizing element) (3-1) included in the
upper or bottom polarizer comprises a iodine-based compound or a
dichroic polarizing material arranged in certain direction, and
protective films (3-2, 3-3) for protecting the polarizing film are
formed on the upper part and the bottom part. In addition,
additionally functional films such as an antireflective film (3-4)
may be formed on the polarizer.
Such a polarizer is usually attached to a liquid crystal panel via
a pressure sensitive adhesive (b). Here, said upper polarizer (3)
is not directly attached to the liquid crystal panel, but following
first forming an ITO thin film (a) thereon, it is attached
thereto.
The reason for forming the ITO thin film (a) between the liquid
crystal panel and the upper polarizer is to solve problems such as
malfunction of devices or stains by static electricity generated in
procedures of preparing or using liquid crystal displays.
That is, much static electricity is often generated in a process of
peeling off a release film on a pressure sensitive adhesive of the
polarizer, to attach it to the outside surface of the liquid
crystal panel, and also preparation or use procedures. Such
generated static electricity affects arrangement of the liquid
crystal layer to deteriorate quality of products or induce
malfunction of devices. Therefore, to prevent this problem, static
electricity is prevented by forming the ITO layer via vapor
deposition processes using sputtering equipments and attaching the
polarizer on the upper part of such formed ITO layer.
Demand for preventing such static electricity is important,
particularly, in the above described IPS-LCD. That is, as both of
pixel electrodes and common electrodes in the IPS liquid crystal
panel are formed on only the array substrate of the bottom
substrate, static electricity generation is particularly
problematic in a process of attaching the polarizer to the outside
surface of the upper substrate (color filter substrate).
However, with regard to said ITO, there are concerns about demand
and supply difficulty and cost increase, and the like, due to
depletion of raw materials in future. In addition, since equipments
for vapor depositing ITO thin films are expensive, there is a
problem that the unit cost of production increases.
Therefore, such an alternative that the ITO layer is not totally
formed on the liquid crystal panel, but partially formed thereon,
is practiced. Ultimately, it is required to develop techniques
being capable to obtain the desired antistatic performance without
using said ITO layer.
DISCLOSURE
Technical Problem
The present invention is intended to provide a polarizer which may
solve problems such as malfunction of devices by static electricity
and generation of electrostatic stains and has excellent physical
properties such as endurance reliability under high temperature or
high humidity condition and optical characteristics, without
forming an ITO thin layer on a liquid crystal panel, and a liquid
crystal display comprising the same.
Technical Solution
The present invention provides, as means for solving said problem,
a polarizer comprising a polarizing film or a polarizing element; a
protective film formed on the upper part and the bottom part of
said polarizing film or polarizing element; and a pressure
sensitive adhesive layer formed on the bottom part of said bottom
protective film, wherein an antistatic layer is formed on the upper
or bottom part of said protective film.
The present invention provides, as other means for solving said
problem, a liquid crystal display comprising a liquid crystal panel
including a liquid crystal layer formed between the upper substrate
and the bottom substrate, and
the polarizer, according to the present invention, that is directly
attached to the upper substrate of said liquid crystal panel.
Advantageous Effects
The present invention may provide a polarizer which may prevent
malfunction of devices by static electricity generated in
preparation or use procedures or electrostatic stains, and the
like, without using the ITO layer that is conventionally formed
between the upper glass substrate of a liquid crystal panel and a
polarizer in a liquid crystal display for an antistatic purpose,
and has excellent physical properties such as endurance reliability
under high temperature or high humidity condition and optical
characteristics, and a liquid crystal display thereof.
BEST MODE
The present invention provides a polarizer comprising a polarizing
film or a polarizing element; a protective film formed on the upper
part and the bottom part of said polarizing film or polarizing
element; and a pressure sensitive adhesive layer formed on the
bottom part of said bottom protective film, wherein an antistatic
layer is formed on the upper or bottom part of said protective
film.
The polarizer of the present invention is described in more detail
below.
The polarizer of the present invention comprises an antistatic
layer (c) formed on the upper part and/or the bottom part of
protective films (3-2, 3-3) as represented in the attached FIGS. 2
to 7.
Said antistatic layer (c) may be included in the polarizer as a
single layer as in FIGS. 2 to 4, two or more layers may be formed
on appropriate positions as represented in FIGS. 5 and 6 and, if
appropriate, the upper part and the bottom part of the upper and
bottom protective films (3-2, 3-3) may be formed at the same time
as represented in FIG. 7. Numbers and positions for forming said
antistatic layer (c) herein is not particularly limited, and may be
appropriately selected depending on use of applying the
polarizer.
The polarizing film or polarizing element included in the polarizer
of the present invention may be selected from general films or
elements known in this field, without particularly limiting any
kind. In the present invention, for example, films or elements as
prepared by containing polarizing components such as iodine or a
dichroic dye in a film based on polyvinyl alcohol resin, and then
elongating the film, may be used, as said polarizing film or
element. Here, the polyvinyl alcohol resin which may be used
includes, but does not limited to, polyvinyl alcohol, polyvinyl
formal, polyvinyl acetal or saponified products of ethylene-vinyl
acetate copolymer. Polymerization degree of said polyvinyl alcohol
resin may be 100 to 5,000, preferably 1,400 to 4,000. In addition,
a thickness of said polarizing film or element herein may be
appropriately selected depending on use of applying the polarizer.
The polarizing film or element may be usually formed in a thickness
of about 5 .mu.m to 80 .mu.m, to which the scope of the present
invention is not limited.
The polarizer of the present invention may comprise protective
films formed on the upper part and the bottom part of said
polarizing film or element. Without particularly limiting any kind
of said protective film herein, for example, cellulose film such as
triacetyl cellulose; polyester film such as polyethylene
terephthalate film; polycarbonate film; polyether sulfonate film;
acrylic film and/or polyolefin film such as polyethylene film,
polypropylene film, polyolefin film containing cyclo or norbornene
structure or ethylene-propylene copolymer film may be used.
The thickness of said protective film included in the polarizer
herein is also not particularly restricted, and the film may be
formed in a usual thickness.
A method of attaching the protective film to said polarizing film
or element herein is not particularly limited, and, for example,
the film may be attached using known adhesion means such as
polyvinyl alcohol adhesives containing polyvinyl alcohol resin and
a crosslinking agent, and the like.
The antistatic layer included in the polarizer of the present
invention may have a surface resistance of
10.sup.10.OMEGA./.quadrature. or less, preferably
10.sup.9.OMEGA./.quadrature. or less and more preferably
10.sup.8.OMEGA./.quadrature. or less. If the surface resistance of
said antistatic layer is in excess of
10.sup.10.OMEGA./.quadrature., it is apprehended that antistatic
performance will be deteriorated. In addition, the lower limit of
surface resistance in said antistatic layer herein is not
particularly restricted, and may be suitably regulated in a range
of, for example, 10.sup.4.OMEGA./.quadrature. or more. If the
surface resistance of the antistatic layer herein is excessively
lowered, it is apprehended that as the content of conductive
materials included in the antistatic layer increases, endurance
reliability under high temperature or high humidity, transparence,
optical characteristics, and the like will be deteriorated, or
adherence of the antistatic layer with other layers will be
lowered.
However, the surface resistance of said antistatic layer is merely
one example of the present invention. That is, the value of surface
resistance in said antistatic layer may be suitably controlled,
considering the number of forming antistatic layers or the value of
surface resistance in a conductive pressure sensitive adhesive
layer, which is described below.
The antistatic layer of the present invention may comprise a binder
resin and a conductive material. Specifically, the antistatic layer
may be formed by dispersing certain conductive material in a
composition being capable of forming a binder resin to prepare a
coating material, and then coating said coating material on the
desired position and curing it.
Any kind of the binder resin, which may be used herein, is not
particularly limited, as long as it may have excellent transparence
in cured state, and excellent adherence with a film (for example,
polarizing film or element, protective film, and the like) included
in the polarizer and effectively maintain a conductive material
dispersed inside.
For example, acrylic resins, epoxy resins, urethane resins, phenol
resins or polyester resins, and the like, and more preferably,
acrylic resins may be used herein as said binder resin.
Specifically, it is preferred herein to use a light curable (for
example, UV curable) binder resin as said binder resin.
By using such light curable type binder resin, the antistatic layer
may be formed harder, whereby the conductive material included
inside is maintained more stably, and thus, a problem, which causes
change of surface resistance over time in the antistatic layer, may
be prevented. In addition, by using the light curable type binder
resin, viscosity may be easily controlled in a process of forming
the antistatic layer, and by omitting an aging process, ant the
like, workability and productivity may be outstandingly
improved.
For example, the light curable binder resin as above herein, may be
prepared by curing a resin composition comprising a multifunctional
monomer or oligomer; and a photoinitiator.
As said multifunctional monomer or oligomer, for example,
multifunctional acrylate, preferably, trifunctional or more
multifunctional acrylate may be used, without particularly limiting
any kind.
Specific examples of usable multifunctional acrylate herein may
include, but do not limited to, difunctional acrylate such as
1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,
neopentyl glycol di(meth)acrylate, polyethylene glycol
di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate,
hydroxyl pivalic acid neopentyl glycol di(meth)acrylate,
dicyclopentanyl di(meth)acrylate, caprolactone modified
dicyclopentenyl di(meth)acrylate, ethyleneoxide modified
di(meth)acrylate, di(meth)acryloxy ethyl isocyanurate, allylated
cyclohexyl di(meth)acrylate,
tricyclodecanedimethanol(meth)acrylate, dimethylol dicyclopentane
di(meth)acrylate, ethyleneoxide modified hexahydrophthalic acid
di(meth)acrylate, tricyclodecane dimethanol(meth)acrylate,
neopentyl glycol modified trimethylpropane di(meth)acrylate,
adamantane di(meth)acrylate or
9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene); trifunctional
acrylate such as trimethylolpropane tri(meth)acrylate,
dipentaerythritol tri(meth)acrylate, propionic acid modified
dipentaerythritol tri(meth)acrylate, pentaerythritol
tri(meth)acrylate, propyleneoxide modified trimethylolpropane
tri(meth)acrylate, trifunctional urethane(meth)acrylate or
tris(meth)acryloxyethylisocyanurate; tetrafunctional acrylates such
as digylcerin tetra(meth)acrylate or pentaerythritol
tetra(meth)acrylate; pentafunctional acrylated such as propionic
acid modified dipentaerythritol penta(meth)acrylate; and
hexafunctional acrylate such as dipentaerythritol
hexa(meth)acrylate, caprolactone modified dipentaerythritol
hexa(meth)acrylate or urethane(meth)acrylate (for example, reaction
products of isocyanate monomer and trimethylolpropane
tri(meth)acrylate, and the like) (for example, UA-306I or UA-306T
from Kyoeisha).
In addition, as the photoinitiator which may be used in the present
invention, for example, benzoin, benzoin methylether, benzoin
ethylether, benzoin isopropylether, benzoin n-butylether, benzoin
isobutylether, acetophenone, dimethylamino acetophenone,
2,2-dimethoxy-2-phenylacetophenone,
2,2-diethoxy-2-phenylacetophenone,
2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl
ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl) ketone,
benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone,
dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone,
2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone,
2-ethylthioxanthone, 2-chlorothioxanthone,
2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl
ketal, acetophenone dimethyl ketal, p-dimethylamino benzoic acid
ester,
oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] and
2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide may be used,
without particularly limiting any kind, among which one kind or two
or more kinds may be used.
The resin composition forming the binder resin herein preferably
comprises said photoinitiator in an amount of 1 part by weight to
20 parts by weight, relative to 100 parts by weight of a
multifunctional monomer or oligomer. If the amount of said
photoinitiator is less than 1 part by weight, it is apprehended
that efficient curing reaction will be not carried out. If the
amount is in excess of 20 parts by weight, it is apprehended that
physical properties such as durability or transparency of the
antistatic layer will be deteriorated, due to the remaining
components.
In addition, the condition that said resin composition is subjected
to light curing (for example, UV curing) to prepare the binder
resin herein is not particularly restricted, and may be suitably
controlled, considering composition of said resin composition.
As examples of conductive materials included in the antistatic
layer together the binder resin as above herein, metals, metal
oxides or alloy materials such as ITO (tin-doped indium oxide), AZO
(antimony-doped zinc oxide), ATO (antimony-doped tin oxide), SnO,
RuO.sub.2, IrO.sub.2, gold, silver, nickel, copper and palladium;
or conductive polymers such as polyaniline, polyacetylene,
polypyrrole, polythiophene, polyparaphenylene, polydienylene,
polyphenylene vinylene, polyphenylene sulfide or polysulfurnitride
may be used. As conductive materials herein, conductive materials
in which the above described metals, metal oxides or alloy
materials is vapor deposited on a surface of a core consisting of
polymers as described above and the like to form a shell may be
also used. Said conductive materials herein may be used alone or in
combination of two or more kinds thereof.
An amount of said conductive materials herein may vary with
conductivity to be secured, but be controlled in an amount of 10
parts by weight to 80 parts by weight, relative to 100 parts by
weight of the aforementioned binder resin. If said amount is less
than 10 parts by weight, it is apprehended that electric
conductivity will not be obtained. If said amount is in excess of
80 parts by weight, it is apprehended that compatibility with the
binder resin will be lowered, or transparence or durability of the
antistatic layer will be deteriorated.
The present polarizer comprises a pressure sensitive adhesive layer
formed on the bottom part of a bottom protective film, which serves
to be capable of attaching the polarizer to a liquid crystal panel,
together with the aforementioned components. Preferably, as said
pressure sensitive adhesive layer, a conductive pressure sensitive
adhesive layer is used, which is not particularly limited
thereto.
Said conductive pressure sensitive adhesive included in the present
polarizer may have a surface resistance of
10.sup.12.OMEGA./.quadrature. or less, preferably
10.sup.11.OMEGA./.quadrature. or less. If the surface resistance of
said pressure sensitive adhesive is in excess of
10.sup.12.OMEGA./.quadrature., it is apprehended that antistatic
performance represented in the polarizer will be lowered. The lower
limit of surface resistance of said pressure sensitive adhesive
herein is not particularly limited, and may be controlled in a
range of, for example, 10.sup.6.OMEGA./.quadrature. or more,
preferably more than 9.9.times.10.sup.7.OMEGA./.quadrature.. If the
surface resistance in the conductive pressure sensitive adhesive
layer is set extremely low, it is apprehended that physical
properties such as endurance reliability and optical
characteristics of liquid crystal displays will be deteriorated due
to increase of antistatic amounts included in the pressure
sensitive adhesive layer.
Said pressure sensitive adhesive layer herein may have the gel
content, represented in the following Equation 1, of 5% to 95%,
preferably 30% to 95%, more preferably 40% to 95%, and most
preferably 60% to 85%. Gel Content (%)=B/A.times.100 [Equation
1]
wherein, A represents weight of said conductive pressure sensitive
adhesive, and B represents dry weight of undissolved conductive
pressure sensitive adhesive after immersing it in ethyl acetate at
room temperature for 72 hours.
The term "dry weight" used herein refers to a weight of undissolved
conductive pressure-sensitive adhesve itself obtained by drying the
immersed conductive pressure-sensitive adhesve in a suitable
condition after the aforementioned immersing process in order to
remove ethyl acetate ingredient included therein. Here, the drying
condition for removing ethyl acetate is not particularly limited,
as long as drying is carried out to be capable of removing ethyl
acetate included in the immersed conductive pressure-sensitive
adhesve.
If the gel content of the pressure sensitive adhesive layer herein
is less than 5%, it is apprehended that endurance reliability will
be lowered, such that bubbles are generated in high temperature or
high humidity condition. If it is in excess of 95%, it is
apprehended that peeling or looseness phenomenon, and the like will
be caused in high temperature or high humidity condition.
The components consisting of pressure sensitive adhesive layers
herein are not particularly limited. For example, as said pressure
sensitive adhesive layer herein, a cured product of a composition
comprising a pressure sensitive base resin and an antistatic agent
may be used.
Without particularly limiting any kind of the pressure sensitive
base resin herein, preferably, a base resin having a weight average
molecular weight (M.sub.w) of 500,000 to 2,500,000, preferably
800,000 to 2,000,000 may be used. If the weight average molecular
weight of said resin is less than 500,000, it is apprehended that
endurance reliability will be lowered, such that bubbles or peeling
phenomenon is caused in high temperature or high humidity
condition. If it is in excess of 2,500,000, the adherence property
will be lowered.
Preferably, said base resin used herein may have a glass transition
temperature of -60.degree. C. to 15.degree. C. If the glass
transition temperature of the base resin herein is less than
-60.degree. C., it is apprehended that elastic modulus of the
pressure sensitive adhesive layer will be extremely lowered. If it
is in excess of 15.degree. C., it is apprehended that endurance
reliability of the liquid crystal display will be lowered due to
decrease of adherence.
For example, as the above base resin herein, a polymer of a monomer
mixture comprising 90 parts by weight to 99.9 parts by weight of
(meth)acrylic acid ester monomer; and 0.01 parts by weight to 10
parts by weight of a crosslinkable monomer may be used.
Without particularly limiting any kind of the (meth)acrylic acid
ester monomer included in the monomer mixture herein, for example,
alkyl(meth)acrylate may be used. If the alkyl group included in the
monomer has much long chain, cohesive attraction of the pressure
sensitive adhesive is lowered and glass transition temperature
(T.sub.g) and adherence are hard to control. Therefore, it is
preferred to use alkyl(meth)acrylate having an alkyl group of 1 to
14 carbon atoms. Examples of such a monomer herein may include
methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate,
isopropyl(meth)acrylate, n-butyl(meth)acrylate,
t-butyl(meth)acrylate, sec-butyl(meth)acrylate,
pentyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,
2-ethylbutyl(meth)acrylate, n-octyl(meth)acrylate,
isooctyl(meth)acrylate, isononyl(meth)acrylate,
lauryl(meth)acrylate and tetradecyl(meth)acrylate and use alone or
in combination of two or more species thereof. It is preferred that
such a (meth)acrylic acid ester monomer in the monomer mixture is
included in an amount of 90 parts by weight to 99.9 parts by
weight, relative to the aforementioned crosslinkable monomer. If
said amount is less than 90 parts by weight, it is apprehended that
the initial bond strength of the pressure sensitive adhesive will
be lowered. If it is in excess of 99.9 parts by weight, it is
apprehended that a problem with durability will occur due to
decrease of cohesive attraction.
The crosslinkable monomer herein may give the pressure sensitive
adhesive cohesive attraction and serve to control adhesive strength
and endurance reliability, and the like under high temperature or
high humidity condition. Examples of such a crosslinkable monomer
may include one or two or more of a monomer containing a hydroxyl
group, a monomer containing a carboxyl group and a monomer
containing nitrogen. Examples of said monomer containing a hydroxy
group may include one or two or more of
2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,
4-hydroxybutyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate,
8-hydroxyoctyl(meth)acrylate, 2-hydroxyethylene
glycol(meth)acrylate or 2-hydroxypropylene glycol(meth)acrylate,
examples of the monomer containing a carboxyl group may include one
or two or more of acrylic acid, methacrylic acid,
2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propionate,
4-(meth)acryloyloxy butyrate, acrylic acid dimmer, itaconic acid,
maleic acid or maleic anhydride, and examples of the monomer
containing nitrogen may include one or two or more of
(meth)acrylamide, N-vinyl pyrrolidone or N-vinylcaprolactam, but
each is not limited thereto. Here, each may be used alone or in
combination of two or more species thereof.
In the monomer mixture, said crosslinkable monomer may be included
in an amount of 0.01 parts by weight to 10 parts by weight,
relative to the aforementioned (meth)acrylic acid ester monomer. If
said amount is less than 0.01 parts by weight, it is apprehended
that endurance reliability of the pressure sensitive adhesive layer
will be lowered. If it is in excess of 10 parts by weight, it is
apprehended that adherence or peeling strength will be lowered.
Said monomer mixture herein may further comprise a compound
represented by the following Formula 1. Said compound may be added
to give the pressure sensitive adhesive control of glass transition
temperature and other functions.
##STR00001##
wherein, R.sub.1 to R.sub.3 each represent independently hydrogen
or alkyl, and R.sub.4 represents cyano; phenyl unsubstituted or
substituted with alkyl; acetyloxy; or COR.sub.5, where R.sub.5
represents a glycidyloxy or amino unsubstituted or substituted with
alkyl or alkoxyalkyl.
In definitions of R.sub.1 to R.sub.5 of said formula, alkyl or
alkoxy means alkyl or alkoxy having 1 to 8 carbon atoms, and is,
preferably, methyl, ethyl, methoxy, ethoxy, propoxy or butoxy.
Specific examples of said compound of Formula 1 may include one or
two or more of a monomer containing nitrogen such as
(meth)acrylonitrile, (meth)acrylamide, N-methyl(meth)acrylamide or
N-butoxymethyl(meth)acrylamide; styrene monomer such as styrene or
methyl styrene; glycidyl(meth)acrylate; or carbonic acid vinyl
ester such as vinyl acetate, but are not limited thereto. When the
above compound is included in the monomer mixture, its amount is,
preferably, 20 parts by weight or less, relative to (meth) acryl
ester monomer or crosslinkable monomer. If said amount is in excess
of 20 parts by weight, it is apprehended that flexibility or
peeling strength of pressure sensitive adhesives will be
lowered.
A method of polymerizing said monomer mixture containing each
component is not particularly limited, wherein the polymer may be
prepared via general polymerization, such as solution
polymerization, photopolymerization, bulk polymerization,
suspension polymerization or emulsion polymerization. Especially,
it is preferred herein to use solution polymerization. Here, it is
preferred to carry out the solution polymerization at a
polymerization temperature of 50.degree. C. to 140.degree. C.,
following mixing an initiator in a condition that each component is
homogeneously mixed. The usable initiator may include usual
initiators, for example, azo polymerization initiators such as
azobisisobutyronitrile or azobiscyclohexane carbonitrile; and/or
peroxides such as benzoyl peroxide or acetyl peroxide, and the
like.
The present conductive pressure sensitive adhesive may comprise an
antistatic agent together with said base resin. The usable
antistatic agent herein is not particularly limited, as long as it
may have excellent compatibility with the aforementioned base
resin, and give antistatic performance thereto, without affecting
any adverse effect on all physical properties such as transparence,
workability and endurance reliability of pressure sensitive
adhesives.
Examples of the usable antistatic agent herein may include
inorganic salts or organic salts, and the like.
In accordance with the present invention, cations included in said
inorganic salt may be alkali metal cations or alkali earth metal
cations. Here, specific examples of said cation may include one or
two or more of lithium ion (Li.sup.+), sodium ion (Na.sup.+),
potassium ion (K.sup.+), rubidium ion (Rb.sup.+), cesium ion
(Cs.sup.+), beryllium ion (Be.sup.2+), magnesium ion (Mg.sup.2+),
calcium ion (Ca.sup.2+), strontium ion (Sr.sup.2+) and barium ion
(Ba.sup.2+), and the like. Preferably, one or two or more of
lithium ion (Li.sup.+), sodium ion (Na.sup.+), potassium ion
(K.sup.+), cesium ion (Cs.sup.+), beryllium ion (Be.sup.2+),
magnesium ion (Mg.sup.2+), calcium ion (Ca.sup.2+) and barium ion
(Ba.sup.2+) may be used and more preferably, lithium ion (Li.sup.+)
may be used in view of ion stability, and mobility in the pressure
sensitive adhesive layer, but they are not limited thereto.
Said organic salts herein may comprise onium cations. The term
"onium cations" as used herein may refer to positively (+) charged
ions in which at least part of charges are localized in at least
one atom selected from the group consisting of nitrogen (N),
phosphorus (P) and sulfur (S). Said onium cations herein may be a
cyclic or noncyclic compound, wherein the cyclic compound may be a
nonaromatic or aromatic compound. In addition, said cyclic compound
may contain at least one heteroatom (for example, oxygen) rather
than nitrogen, phosphorus or sulfur atom. Said cyclic or noncyclic
compound may be also optionally substituted with substituents such
as hydrogen, alkyl or aryl. Further, said noncyclic compound may
contain at least one, preferably, at least four substituents,
wherein said substituent may be a cyclic or noncyclic substituent,
or an aromatic or nonaromatic substituent.
In one aspect of the present invention, said onium cation may
comprise a nitrogen atom, preferably, be an ammonium ion. Here,
said ammonium ion may be a quaternary ammonium ion or an aromatic
ammonium ion.
Preferably, said quaternary ammonium ion may be a cation
represented in the following Formula 2.
##STR00002##
wherein, R.sub.6 to R.sub.9 each independently represent alkyl,
alkenyl, alkynyl, alkoxy or aryl.
In definitions of R.sub.6 to R.sub.9 in said Formula 2, alkyl,
alkenyl, alkynyl or alkoxy may contain straight, branched or cyclic
structures, and be optionally substituted with a hydroxyl group or
alkyl or alkoxy having 1 to 4 carbon atoms.
In definitions of R.sub.6 to R.sub.9 in said Formula 2, alkyl or
alkoxy may be also alkyl or alkoxy having 1 to 12 carbon atoms, and
preferably, methyl, ethyl, propyl, butyl, hexyl, octyl, methoxy or
ethoxy.
Further, in definitions of R.sub.6 to R.sub.9 in said Formula 2,
alkenyl or alkynyl may be alkenyl or alkynyl having 2 to 12,
preferably 2 to 8, more preferably 2 to 4 carbon atoms, and aryl
may be aryl having 6 to 30, preferably 6 to 20 carbon atoms, and
preferably, phenyl or naphthyl.
Specific examples of said quaternary ammonium ion represented in
Formula 2 may include
N-ethyl-N,N-dimethyl-N-(2-methoxyethyl)ammonium ion,
N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium ion,
N-ethyl-N,N-dimethyl-N-propylammonium ion,
N-methyl-N,N,N-trioctylammonium ion,
N,N,N-trimethyl-N-propylammonium ion, tetrabutylammonium ion,
tetramethylammonium ion, tetrahexylammonium ion and
N-methyl-N,N,N-tributylammonium ion, and the like, but is not
limited thereto.
In addition, examples of said aromatic ammonium ion may include one
or more selected from the group consisting of pyridinium,
pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium,
thiazolium, oxazolium and triazolium, and be preferably one or two
or more of N-alkyl pyridinium substituted, in which the alkyl group
has 4 to 16 carbon atoms, 1,3-alkylmethyl imidazolium, in which the
alkyl group has 2 to 10 carbon atoms and 1,2-dimethyl-3-alkyl
imidazolium, in which the alkyl group has 2 to 10 carbon atoms, but
are not limited thereto.
Preferably, examples of an anion included in inorganic or organic
salts containing said cation in the present antistatic agent are
selected from the group consisting of fluoride (F.sup.-), chloride
(Cr.sup.-), bromide (Br.sup.-), iodide (I.sup.-), perchlorate
(ClO.sub.4.sup.-), hydroxide (OH.sup.-), carbonate
(CO.sub.3.sup.2-), nitrate (NO.sub.3.sup.-), sulfonate
(SO.sub.4.sup.-), methylbenzenesulfonate
(CH.sub.3(C.sub.6H.sub.4)SO.sub.3.sup.-), p-toluenesulfonate
(CH.sub.3C.sub.6H.sub.4SO.sub.3.sup.-), carboxybenzenesulfonate
(COOH(C.sub.6H.sub.4)SO.sub.3.sup.-), trifluoromethanesulfonate
(CF.sub.3SO.sub.2.sup.-), benzonate (C.sub.6H.sub.5COO.sup.-),
acetate (CH.sub.3COO.sup.-), trifluoroacetate (CF.sub.3COO.sup.-),
tetrafluoroborate (BF.sub.4.sup.-), tetrabenzylborate
(B(C.sub.6H.sub.5).sub.4.sup.-), hexafluorophosphate
(PF.sub.6.sup.-), trispentafluoroethyl trifluorophosphate
(P(C.sub.2F.sub.5).sub.3F.sub.3.sup.-),
bistrifluoromethanesulfonimide (N(SO.sub.2CF.sub.3).sub.2.sup.-),
bispentafluoroethanesulfonimide (N(SOC.sub.2F.sub.5).sub.2.sup.-),
bispentafluoroethanecarbonylimide
(N(COC.sub.2F.sub.5).sub.2.sup.-), bisperfluorobutanesulfonimide
(N(SO.sub.2C.sub.4F.sub.9).sub.2.sup.-),
bisperfluorobutanecarbonylimide (N(COC.sub.4F.sub.9).sub.2.sup.-),
tristrifluoromethanesulfonylmethide
(C(SO.sub.2CF.sub.3).sub.3.sup.-), and
tristrifluoromethanecarbonylmethide
(C(SO.sub.2CF.sub.3).sub.3.sup.-), but are not limited thereto.
Preferably, an imide anion which serves better to be electron
withdrawing and is substituted with fluorine having good
hydrophobicity to have high ion stability is used, without limiting
thereto.
It is preferred that said inorganic or organic salt in the pressure
sensitive adhesive layer is included in an amount of 0.1 parts by
weight to 50 parts by weight, relative to 100 parts by weight of
the base resin. If said amount is less than 0.1 parts by weight, it
is apprehended that the desired antistatic effect will be not
obtained. If it is in excess of 50 parts by weight, it is
apprehended that compatibility with the base resin, endurance
reliability or transparence will be deteriorated.
In addition, the present pressure sensitive adhesive may further
comprise a coordination bond compound together with said antistatic
agent. The term "coordination bond compound" used herein means a
compound having at least one functional group which is capable of
forming coordination bond with the cation included in the
aforementioned antistatic agent, preferably the inorganic salt.
Such a coordination bond compound may couple with a cation in the
antistatic agent to form a stable complex compound, whereby small
quantity of antistatic agent is used, so that by increasing anion
concentration inside the pressure sensitive adhesive, ion
conductivity can be more effectively given, while maintaining and
improving physical properties such as compatibility with the base
resin, endurance reliability and transparence.
As long as the usable coordination bond compound herein has a
functional group to be capable of bonding coordination in the
molecule, it is not particularly limited thereto.
For example, as said coordination bond compound herein, one or two
or more of a compound containing an oxalate group, a compound
containing a diamine group, a compound containing a polycarboxyl
group, a compound containing a .beta.-ketone group and a compound
containing an oxime group may be used. Among these, a compound
containing an oxalate group is rather preferred, but not limited
thereto. It is preferred that said compound is included in an
amount of 0.1 parts by weight to 10 parts by weight, relative to
100 parts by weight of the aforementioned base resin. If said
amount is less than 0.1 parts by weight, it is apprehended that the
effect of improving antistatic performance will be lowered. If it
is in excess of 10 parts by weight, endurance reliability of the
pressure sensitive adhesive, and the like will be lowered.
For example, said compound containing an oxalate group may be a
compound represented by the following Formula 3.
##STR00003##
wherein, R.sub.10 and R.sub.11 each independently represent
hydrogen, halogen, alkyl, alkoxy, alkenyl, alkynyl, aryl, arylalkyl
or aryloxy.
In definitions of said Formula 3, alkyl, alkoxy, alkenyl or alkynyl
may have straight, branched or cyclic structures.
In definitions of said Formula 3, alkyl or alkoxy may be also alkyl
or alkoxy having 1 to 20, preferably 1 to 12, more preferably 1 to
8, and most preferably 1 to 4 carbon atoms.
Further, in definitions of said Formula 3, alkenyl or alkynyl may
be alkenyl or alkynyl having 2 to 12, preferably 2 to 8, more
preferably 2 to 4 carbon atoms, and aryl may be aryl having 6 to
30, preferably 6 to 20 carbon atoms, preferably phenyl or
naphthyl.
Specific examples of said compound represented by Formula 3 may
include one or two or more of diethyloxalate, dimethyloxalate,
dibutyloxalate, di-tert-butyloxalate and
bis(4-methylbenzyl)oxalate, but are not limited thereto.
For example, said compound containing a diamine group may be
represented by the following Formula 4.
##STR00004##
wherein, R.sub.12 represents alkylene or alkenylene.
In definitions of said Formula 4, alkylene may be alkylene having 1
to 12, preferably 1 to 8 carbon atoms, and alkenylene may be
alkenylene having 2 to 10, preferably 2 to 8 carton atoms.
In definitions of said Formula 4, alkylene or alkenylene may also
have straight, branched or cyclic structures.
Specific examples of said compound represented by Formula 4 may
include one or two or more of ethylenediamine, 1,2-diaminopropane
or diaminobutane, but are not limited thereto.
In addition, said compound containing a polycarboxyl group may be,
for example a compound containing a functional group represented by
the following Formulas 5 to 7 as a compound containing
polycarboxylic acid or carboxylate.
##STR00005##
Specific examples of said compound containing a polycarboxyl group
may include ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA),
N,N,N',N'',N''-diethylenetriaminepentaacetic acid (DTPA),
1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetracetic acid
(DOTA), 1,4,7,10-tetraazacyclododecane-N,N',N''-triacetic acid
(DO3A), trans(1,2)-cyclohexanodiethylenetriaminepentaacetic acid or
N,N-biscarboxymethylglycine alone or in combination of two or more
thereof, but are not limited thereto.
In addition, said compound containing a polycarboxyl group may be a
compound represented by the following Formulas 8 to 12.
##STR00006##
For example, said compound containing a .beta.-ketone group may be
a compound represented by the following Formula 13.
##STR00007##
wherein, R.sub.13 and R.sub.14 each independently represent alkyl,
alkoxy, alkenyl, alkynyl, aryl, arylalkyl or aryloxy, and R.sub.15
represents hydrogen, alkyl, alkoxy, alkenyl, alkynyl, aryl,
arylalkyl or aryloxy.
In definitions of said Formula 13, alkyl, alkoxy, alkenyl or
alkynyl may have straight, branched or cyclic structures.
In definitions of said Formula 13, alkyl or alkoxy may be also
alkyl or alkoxy having 1 to 20, preferably 1 to 12, more preferably
1 to 8, and most preferably 1 to 4 carbon atoms.
Further, in definitions of said Formula 13, alkenyl or alkynyl may
be alkenyl or alkynyl having 2 to 12, preferably 2 to 8, more
preferably 2 to 4 carbon atoms, and aryl may be aryl having 6 to
30, preferably 6 to 20 carbon atoms, preferably phenyl or
naphthyl.
Specific examples of said compound of Formula 13 being capable of
being used herein may include one or two or more of 2,4-pentadione,
1-benzoylacetone or ethylacetoacetate, but are not limited
thereto.
Further, the usable coordination bond compound herein may be a
compound containing ether bonds which forms a complex with the
aforementioned inorganic salt to provide ion stability and to
achieve a stable structure, and such a compound may be represented
by, for example, the following Formula 14.
##STR00008##
wherein, R.sub.16 and R.sub.17 each independently represent alkyl
or aryl, R.sub.18 represents hydrogen or alkyl, and n is an integer
of 2 to 20.
In definitions of substituents in said Formula 14, alkyl may
represent alkyl having 1 to 20, preferably 4 to 12 carbon atoms,
and aryl may represent aryl having 6 to 20, preferably 6 to 12
carbon atoms, and more preferably, phenyl or naphthyl.
Specific examples of said compound of Formula 14 being capable of
being used herein may included diethylene glycol
di-2-ethylhexonate, tetraethylene glycol di-2-ethylhexonate,
polyethylene glycol di-2-ethylhexonate, triethylene glycol
diethylbutylate, polyethylene glycol diethylbutylate, polypropylene
glycol diethylhexonate, triethylene glycol dibenzoate,
tetraethylene glycol dibenzoate, polyethylene glycol dibenzoate,
polypropylene glycol dibenzoate or polyethylene
glycol-2-ethylhexonate benzoate, and the like alone or in
combination of two or more thereof, but are not limited
thereto.
It is preferred that said compound of Formula 14 is also included
in an amount of 0.01 parts by weight to 10 parts by weight,
relative to 100 parts by weight of the aforementioned base resin.
If said amount is less than 0.01 parts by weight, it is apprehended
to have a slight effect on improving antistatic performance. If it
is in excess of 10 parts by weight, it is apprehended that cohesive
attraction and pressure sensitive durability, and the like will be
deteriorated.
The present conductive pressure sensitive adhesive may further
comprise 0.1 parts by weight to 10 parts by weight of a
crosslinking agent, relative to 100 parts by weight of the base
resin, together with the aforementioned components. Such a
crosslinking agent may give the pressure sensitive adhesive
cohesive attraction via a crosslinking reaction with a
crosslinkable functional group included in the base resin.
Here, without particularly limiting any kind of specific
crosslinking agents to be used, general crosslinking agents, such
as isocyanate compounds, epoxy compounds, aziridine compounds and
metal chelate compounds, may be used.
Examples of said isocyanate compounds may include one or more
selected from the group consisting of tolylene diisocyanate, xylene
diisocyanate, diphenylmethane diisocyanate, hexamethylene
diisocyanate, isophorone diisocyanate, tetramethylxylene
diisocyanate, naphthalene diisocyanate and a reaction product of
polyol (for example, tremethylol propane) with any one of
isocyanate compounds thereof; examples of the epoxy compounds may
include one or more selected from the group consisting of ethylene
glycol diglycidylether, triglycidylether, trimethylolpropane
triglycidylglycidylether, N,N,N',N'-tetraglycidyl ethylenediamine
and glycerine diglycidylether; and examples of the aziridine
compounds may include one or more selected from the group
consisting of N,N'-toluene-2,4-bis(1-aziridinecarboxamide),
N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), triethylene
melamine, bisisophthaloyl-1-(2-methylaziridine) and
tri-1-aziridinylphosphineoxide. Further, as examples of said metal
chelate compounds, a compound in which a polyvalent metal such as
aluminum, iron, zinc, tin, titanium, antimony, magnesium and/or
vanadium coordinates to acetyl acetone or ethyl acetoacetate, and
the like may be used, but they are not limited thereto.
It is preferred that said crosslinking agent is included in an
amount of 0.1 parts by weight to 10 parts by weight, relative to
100 parts by weight of the aforementioned base resin. If said
amount is less than 0.1 parts by weight, it is apprehended that
cohesive attraction of the pressure sensitive adhesive will be
lowered. If it is in excess of 10 parts by weight, it is
apprehended that endurance reliability will be lowered, since
interlayer peeling or loosing phenomenon is caused.
The present pressure sensitive adhesive may further comprise 0.01
parts by weight to 10 parts by weight of a silane coupling agent,
relative to 100 parts by weight of the base resin, in addition to
the aforementioned components. The silane coupling agent may
contribute to enhancement of attachment reliability, when the
pressure sensitive adhesive is left in high temperature or high
humidity condition for a long time, and may improve adhesion
stability on attaching to the glass substrate to enhance heat
resistance and humidity resistance. Examples of the silane coupling
agent to be capable of being used herein may include
.gamma.-glycidoxypropyltrimethoxysilane,
.gamma.-glycidoxypropylmethyldiethoxysilane,
.gamma.-glycidoxypropyltriethoxysilane,
3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane,
vinyltriethoxysilane, .gamma.-methacryloxypropyltrimethoxysilane,
.gamma.-methacryloxypropyltriethoxysilane,
.gamma.-aminopropyltriethoxysilane,
3-isocyanatepropyltriethoxysilane and
.gamma.-acetoacetatepropyltrimethoxysilane alone or in combination
of two or more thereof, but are not limited thereto.
The silane coupling agent is included in an amount of, preferably,
0.01 parts by weight to 10 parts by weight, more preferably, 0.05
parts by weight to 1 part by weight, relative to 100 parts by
weight of the base resin. If said amount is less than 0.01 parts by
weight, it is apprehended to have a slight effect on increasing
adhesion strength. If it is in excess of 10 parts by weight, it is
apprehended that endurance reliability will be lowered, since
bubbles or peeling phenomenon is caused.
In addition, the present pressure sensitive adhesive may further
comprise 1 part by weight to 100 parts by weight of a tackifier
resin, relative to 100 parts by weight of the base resin, in view
of controlling adhesion performance. Without particularly limiting
any kind of such a tackifier resin, for example, (hydrogenated)
hydrocarbon resins, (hydrogenated) rosin resins, (hydrogenated)
rosin ester resins, (hydrogenated) terpene resins, (hydrogenated)
terpene phenol resins, polymerized rosin resins or polymerized
rosin ester resins, and the like may be used alone or in a mixture
of two or more thereof. If said amount of the tackifier resin is
less than 1 part by weight, it is apprehended to have a slight
addition effect. If it is in excess of 100 parts by weight, it is
apprehended that the effect on improving compatibility and/or
cohesive attraction will be lowered.
In addition, the present conductive pressure sensitive adhesive may
further comprise at least one additive selected from the group
consisting of an initiator such as a thermal initiator or a
photoinitiator; an epoxy resin; a hardner; a ultraviolet light
stabilizer; an antioxidant; a toning agent; a reinforcing agent; a
filler; an antifoamer; a surfactant; a photopolymerizable compound
such as a multifunctional acrylate; and a plasticizer in a range
which does not affect on the effect of the present invention.
A method of forming said pressure sensitive adhesive on a polarizer
herein is not particularly limited, and for example, the following
methods may be used: a method of applying a coating liquid or a
pressure sensitive adhesive composition comprising each of the
aforementioned components on a polarizer with a usual means such as
bar coater and curing it, or a method of applying the coating
liquid or the pressure sensitive adhesive composition on a surface
of a releasable substrate once, followed by dryness, and
transferring formed pressures sensitive adhesive using said
releasable substrate to the polarizer to age and cure it, and the
like.
In such a procedure, if the coating liquid or the pressure
sensitive adhesive composition comprises a multifunctional
crosslinking agent, it is preferred that said crosslinking agent is
controlled, in view of homogeneously coating, so that a
crosslinking reaction of functional groups does not proceed on
forming the pressure sensitive adhesive layer. Therefore, the
crosslinking agent may form the crosslinked structure in drying and
ageing procedures after the coating work to improve cohesive
attraction, and enhance adhesion properties and cuttablility of
adhesion products.
Preferably, said procedure of forming the pressure sensitive
adhesive is also carried out after sufficiently removing components
causing bubbles such as volatile components or reaction residues
inside the coating liquid or the pressure sensitive adhesive
composition. That is, if the crosslink density or the molecular
weight is too low and thus the elastic modulus is lowered, it is
apprehended that small bubbles, which are present between the glass
substrate and the pressure sensitive adhesive layer at high
temperature condition, will become large inside to form scattering
bodies.
In addition, the present polarizer may further comprise at least
one functional layer selected from the group consisting of a
protective layer, a reflective layer, an antiglare layer, a
retardation film, a wide viewing angle compensation film and a
brightness improvement film in view of improving additional
functions.
The present invention also relates to a liquid crystal display
comprising a liquid crystal panel including a liquid crystal layer
formed between a upper and a bottom substrates, and the
aforementioned polarizer according to the present invention that is
directly attached to the upper substrate of said liquid crystal
panel.
As described above, the present invention may provide a liquid
crystal display solving problems such as problems such as
malfunction of devices by static electricity generated in
preparation or use procedures and generation of electrostatic
stains and having excellent physical properties such as endurance
reliability under high temperature or high humidity condition and
optical characteristics, by forming an antistatic layer on the
upper part and/or the bottom part of a protective film consisting
of a multilayer structured polarizer, and if necessary, giving
pressure sensitive adhesive layers used in attaching the polarizer
and the liquid crystal panel antistatic properties, without forming
the thin film of the ITO layer essentially used in the conventional
liquid crystal displays.
That is, the term "polarizer directly attached" herein means that
the polarizer according to the present invention is directly
attached onto the upper substrate (for example, color filter
substrate) of a liquid crystal panel on which a conductive layer
such as an ITO layer for antistatic purpose is not formed over the
entire surface.
A liquid crystal panel included in the present liquid crystal
display is not particularly limited to any kind. For example,
various passive matrix scheme, active matrix scheme, IPS mode and
VA mode liquid crystal panels may be used, without limiting any
kind. Preferably, an IPS mode liquid crystal panel may be used. In
the IPS mode liquid crystal panel, both of common electrode and
pixel electrode are formed on the bottom substrate of the panel, so
that static electricity especially causes a problem in a process of
attaching the polarizer, and the like. However, the present
invention may provide a liquid crystal display having physical
properties such as viewing angle characteristics, endurance
reliability and optical characteristics by solving various problems
due to static electricity without forming the ITO layer.
EXAMPLES
The present invention is explained in more detail through the
following examples according to the present invention and
comparative examples regardless of the present invention, to which
the scope of the present invention is not restricted.
Preparation Example 1
Preparation of Antistatic Layer (AS1)
100 g of dipentaerythritol hexaacrylate, 10 g of photoinitiatoer
(IRGACURE 184, manufactured by Ciba Specialty Chemicals), 100 g of
methyl alcohol and 100 g of propyleneglycol monomethyl ether (PGM)
were sufficiently formulated and stirred in an agitator for about 1
hour to be homogeneously mixed. Subsequently, while 40 g of an AZO
dispersion was slowly dropped into the resulting stirred solution,
the mixture was stirred for 1 hour to be sufficiently mixed, and
then the coating solution was prepared. The prepared coating
solution was coated on a triacetylcellulose film with a bar coater
to have a thickness of 5 .mu.m after curing, and the coated film
was dried in an oven at 60.degree. C. for 2 min. Subsequently, the
dried film was cured by irradiating polymerization mercury lamp (UV
source, light quantity: 1 J/cm.sup.2) thereon to prepare an
antistatic layer (AS1).
Preparation Example 2
Preparation of Antistatic Layer (AS2)
100 g of dipentaerythritol hexaacrylate, 10 g of photoinitiatoer
(IRGACURE 184), 100 g of methyl alcohol and 100 g of
propyleneglycol monomethyl ether (PGM) were formulated and stirred
in an agitator for about 1 hour to be sufficiently mixed.
Subsequently, while 20 g of an AZO dispersion was slowly dropped
into the resulting stirred solution, the mixture was stirred for 1
hour to be sufficiently mixed. The resulting coating solution was
coated on a triacetylcellulose film with a bar coater to have a
thickness of 5 .mu.m after curing, dried in an oven at 60.degree.
C. for 2 min, and irradiated with polymerization mercury lamp (UV
source, light quantity: 1 J/cm.sup.2) to form an antistatic layer
(AS2).
Preparation Example 3
Preparation of Antistatic Layer (AS3)
100 g of dipentaerythritol hexaacrylate, 5 g of photoinitiatoer
(IRGACURE 184), 600 g of methyl alcohol and 400 g of
propyleneglycol monomethyl ether (PGM) were formulated and stirred
in an agitator for about 1 hour to be sufficiently mixed.
Subsequently, while 340 g of an AZO dispersion was slowly dropped
into the resulting stirred solution, the mixture was stirred for 1
hour to be sufficiently mixed. The prepared coating solution was
spin coated on a triacetylcellulose film to have a thickness of
several hundreds nm (about 200 nm) after curing. The coated film
was dried in an oven at 60.degree. C. for 2 min and irradiated with
polymerization mercury lamp (UV source, light quantity: 1
J/cm.sup.2) to form an antistatic layer (AS3).
For the above prepared antistatic layers, physical properties were
evaluated by the following methods.
1. Measurement of Surface Resistance
A voltage of 500 V was applied to the prepared antistatic layer
under environment at a temperature of 23.degree. C. and a relative
humidity of 50% for 1 min., and then its surface resistance was
measured using HIRESTA-UP (MCP-HT450, manufactured by Mitsubishi
Chemical Company).
2. Measurement of Transmission and Haze
Transmission and haze of the prepared antistatic layer at a
wavelength band of 400 nm to 700 nm were measured using a hazemeter
(Murakami Color Research Lab).
3. Measurement of Adhesion
The coating film was subjected to a cross cut test (ASTM D 3359) to
test adhesion. Specifically, cutting-plane lines were scribed in
the coating film by 11 lines in each length and breadth at an
interval of 1 mm to form 100 meshes having 1 mm.sup.2. A process of
attaching a cellophane adhesive tape to the surface of the coating
film and rapidly peeling it off was repeated three times, followed
by evaluating adhesion based on the following standard.
.circle-w/dot.: no peeling off the cured film
.largecircle.: less peeling off the cured film
.DELTA.: 10 to 50 meshes of the cured film are peeled off
x: 50 to 100 meshes of the cured film are peeled off
The results as evaluated above were represented in the following
table 1.
TABLE-US-00001 TABLE 1 AS1 AS2 AS3 Surface resistance 2.0 .times.
10.sup.8 4.0 .times. 10.sup.9 3.7 .times. 10.sup.8
(.OMEGA./.quadrature.) Transmission (%) 91.4 92.0 93.0 Haze 0.4 0.4
0.3 Adhesion .circle-w/dot. .circle-w/dot. .circle-w/dot.
Preparation Example 4
Preparation of Pressure Sensitive Adhesive Layer (PSA1)
Preparation of Acrylic Copolymer
A monomer mixture comprising 98.5 parts by weight of n-butyl
acrylate (BA) and 1.5 parts by weight of hydroxyethyl methacrylate
(2-HEMA) was introduced into a 1 L reactor refluxed with nitrogen
gas and fixed with a cooling apparatus to easily control the
temperature, and 100 parts by weight of ethyl acetate (EAc) as a
solvent was introduced thereto. Subsequently, to remove oxygen, the
reactor was purged with nitrogen gas for 1 hour and the temperature
was maintained at 62.degree. C. The mixture was homogenized, and
0.03 parts by weight of azobisisobutyronitrile (AIBN) diluted with
ethyl acetate in a concentration of 50% as a reaction initiator was
introduced thereto to initiate the reaction. Then, the reaction
proceeded for about 8 hours to prepare an acrylic copolymer having
a weight average molecular weight of 1,500,000 and a glass
transition temperature of -53.degree. C.
Formulation of Coating Solution
Relative to 100 parts by weight of the above prepared acrylic
copolymer, 0.5 parts by weight of a crosslinking agent (isocyanate
type, an adduct of tolylenediisocyanate with trimethylolpropane
(TDI-1)), 1.1 parts by weight of lithium bistrifluoromethane
sulfonylimide and 0.3 parts by weight of polyethylene glycol
di-2-ethylhexonate (n=6) were introduced, diluted in an appropriate
concentration, considering the coating ability, and homogeneously
mixed. Subsequently, the prepared coating solution was coated on a
release sheet and dried to obtain a uniform pressure sensitive
adhesive layer having a thickness of 25 .mu.m.
Preparation Examples 5 to 7
Preparation of Pressure Sensitive Adhesive Layer
Pressure sensitive adhesive layers were prepared by the same method
as the above preparation example 4 except that formulation
components were changed as shown in the following table 2 on
preparing the pressure sensitive adhesive layers. In addition, the
method of measuring surface resistance of pressure sensitive
adhesive layers is as shown in that of the antistatic layer.
TABLE-US-00002 TABLE 2 PSA1 PSA2 PSA3 PSA4 Polymer n-BA 98.5 98.5
98.5 94.6 composition AA -- -- -- 5.3 2-HEMA 1.5 1.5 1.5 0.1
Polymer Mw (10,000) 150 150 150 180 Polymer Tg (.degree. C.) -53
-53 -53 -49 Formulation Crosslinking agent 0.5 0.5 0.5 0.5
composition Antistatic A1 1.1 -- 6.2 -- components A2 -- 0.7 -- --
A3 0.3 -- -- -- A4 -- -- 3.1 -- Surface resistance
(.OMEGA./.quadrature.) 1.1 .times. 10.sup.10 2.3 .times. 10.sup.11
3.6 .times. 10.sup.9 8.6 .times. 10.sup.13 n-BA: n-butylacrylate
AA: acrylic acid 2-HEMA: 2-hydroxyethylmethacrylate A1: lithium
bistrifluoromethanesulfonylimide A2: 4-methyl-N-hexylpyridinium
hexafluorophosphate A3: polyethylene glycol di-2-ethylhexonate (n =
6) A4: di-tert-butyloxalate
Example 1
Using the above prepared antistatic layer (AS2), the above prepared
pressure sensitive adhesive layer (PSA1) and the liquid crystal
panel (A type, IPS mode liquid crystal panel) that the ITO thin
film was not formed over the entire surface, a liquid crystal
display having a structure as shown in FIG. 3 was built up.
Examples 2 to 4 and Comparative Example 1
Liquid crystal displays were prepared by the same method as the
above Example 1 except that the antistatic layer, the pressure
sensitive adhesive layer and the structure of liquid crystal
display were changed as shown in the following table 3. In Table 3
below, liquid crystal panel B means the liquid panel (B type, ISO
mode) that the ITO thin film was formed on the upper substrate of
the liquid crystal panel.
TABLE-US-00003 TABLE 3 Exam- Exam- Comparative ple 1 ple 2 Example
3 Example 4 Example 1 LCD Structure FIG. 3 FIG. 3 FIG. 3 FIG. 4 --
Liquid crystal A A A A B panel Antistatic layer AS2 AS3 AS1 AS3 --
Pressure PSA1 PSA2 PSA3 PSA3 PSA4 sensitive adhesive layer
For the above prepared examples, physical properties were evaluated
by the following methods.
1. Endurance Reliability Evaluation
The prepared pressure sensitive adhesive polarizer was tailored in
a size of 262 mm.times.465 mm (width.times.length) to prepare a
sample. Then, the sample was attached to both sides of a glass
substrate (300 mm.times.470 mm.times.0.7
mm=width.times.length.times.height) in a state that optical
absorption axes are crossed to prepare a specimen. The applied
pressure on attaching was about 5 kg/cm.sup.2, and the attaching
work was carried out in a clean room, so that bubbles or foreign
materials were not caused. To examine moisture-heat resistance of
the prepared specimen, said specimen was hold under a condition at
a temperature of 60.degree. C. and a relative humidity of 90% for
1,000 hours, followed by observing whether or not bubbling or
peeling was caused. Further, for thermal resistance, the specimen
was hold at a temperature of 80.degree. C. for 1,000 hours,
followed by observing whether or not bubbling or peeling was
caused. Here, just prior to evaluating the specimen state, the
specimen was hold at room temperature for 24 hours and evaluated.
The evaluation standards were as follows.
.largecircle.: no bubbling or peeling phenomenon
.DELTA.: slight bubbling or peeling phenomenon
x: present bubbling or peeling phenomenon
2. Electrostatic Stain Evaluation
It was observed whether or not electrostatic stains were caused, on
or after a polarizer, on which the pressure sensitive adhesive was
coated, was attached to a liquid crystal cell (32 inches) in a size
of 32 inches (400 mm.times.708 mm). Specifically, when said
polarizer, in which the releasing film was peeled off, was attached
to the liquid crystal cell, it was observed with the naked eye
using a backlight whether or not electrostatic stains (whitening
phenomenon) were caused.
In addition, the liquid crystal cell, to which the polarizer was
attached, was fixed to a module provided with a backlight. Then,
while an ion gun (+20 kv, -25 kv) was scanned by 25 cycles per
second under the drive state, it was observed with the naked eye
whether or not electrostatic stains (whitening phenomenon) were
caused.
Here, the evaluation standards were as follows.
On Releasing the Release Film
.largecircle.: no causing electrostatic stains.
x: electrostatic stains are caused and do not disappear for several
seconds or more.
Application of Ion Gun
.circleincircle.: electrostatic stains disappear within one
second.
.largecircle.: electrostatic stains disappear within 3 seconds.
x: electrostatic stains do not disappear for 3 seconds or more.
The measuring results as above were represented in the following
table 4.
TABLE-US-00004 TABLE 4 Comparative Example 1 Example 2 Example 3
Example 4 Example 1 Endurance Thermal .largecircle. .largecircle.
.largecircle. .largecircle. - .largecircle. Reliability Resistance
Condition Moisture- .largecircle. .largecircle. .largecircle.
.largecircle. .largec- ircle. Heat Resistance Condition
Electrostatic On .circleincircle. .circleincircle. .circleincircle.
.circl- eincircle. .circleincircle. Stain Releasing Release Film On
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
.c- ircleincircle. Scanning Ion Gun
As can be seen from the results of Table 4 above, it could be
identified that although the A type liquid crystal panel without
including the ITO thin film which had been conventionally formed
for antistatic purposes was used, the liquid crystal displays of
examples according to the present invention had excellent endurance
reliability and antistatic characteristics corresponding to those
of Comparative Example 1 using the B type liquid crystal panel on
which the ITO layer was formed. In addition, as can be seen from
the results of Table 1 above, the antistatic layer according to the
present invention had excellent optical characteristics such as
haze value and transmission together with excellent interface
adhesion, and thus did not cause decrease of physical properties
even on applying it to liquid crystal displays.
DESCRIPTION OF DRAWINGS
FIG. 1 is a cross-sectional view showing a structure of a
conventional liquid crystal display.
FIGS. 2 to 7 are cross-sectional views showing liquid crystal
displays according to various aspects of the present invention.
* * * * *